Small-size high-capacity electrical dust precipitator



Sept. 26, 1944. E. H. R. PEGG 2,359,149

SMALL SIZE HIGH CAPACITY ELECTRICAL DUSTPRECIPITATORS Filed Mair 7, 1942 4 Sheets-Sheet l 82 @711 9' y Insulation fnsulazz'an WITNESSES; INVENTOR MM Edward HR. Peyy.

a Z MF ATTOR N EY P E. H. R. PEGG I 2,359,149

SMALL SIZE HIGH CAPACITY ELECTRICAL DUST-PRECIPITATORS Filed May 7, 1942 4 Sheets-sheaf 2 ooooooooooooo oooo O I? 0 0 I ,36 42 as BL? 2/ M ooooooooooooooooooooooo ODOOOODOOOOOOOOOOO OOOOOOOOOODODOOOOO 20 O0O0000000OOOOOOOOOOOOOOOOOOOOOOO II O000000000000OQOOO'OOOOOODOOOQOOOOO 24 oooooooooooooooooiyooooooooooooo 111111;,111111.(1,1,11,11,10,r J I 1 I WITNESSES: INVENTOR 51M mi hty Edward H- R Pe fi W s- 7 ATTORN EY fffffff.'j'fiflll'ffjj if 1:111:11.:jjjj

Sept. 26, 1944. E; H R PEGG 7 2,359,149

SMALL SIZE HIGH CAPACITY ELECTRICAL DUST-PRECIPITATORS Filed May 7, 1942 4 sheets-sneak y lo, I lTr r l 9 102 97 104 r 0 I g 5 105' I i 96' k l 10;? 99 l 103 I ,E I I 9214 a s 92 La 1 I 97 100 105 82 4 92 92) a 1 I I I O [04. fnsula'tl' I 102 JR 106 9/ -,5 m2 100 105 fnsulazz'on 103 3.1: I 84 WITNESSES:

INVENTOR 5.5M Q Edward HR ATTOR N EY Patented Sept. 26, 1944 SMALL-SIZE HIGH-CAPACITY ELECTRICAL DUST PRECIPITATOR Edward H. R. Pegg, Lakewood, Ohio, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 7, 1942, Serial No. 442,052

14 Claims.

provement on a dust-precipitator embodiment shown and claimed in the G. W. Penney patentapplication Serial No. 382,852, filed March 12,

1941, assigned to the'assignee of this application.

An object of this invention is to provide a relatively small-size precipitator of relatively high cleaning capacity.

A further object of this invention is to provide a small-size dust-precipitator which can be easily and cheaply manufactured and assembled.

A further object of my invention is to provide a precipitator-cell comprising a casing having a gas-cleaning or dust-removing means including electrode-means providing an initial dust-charging zone, an intermediate zone in which the relatively larger-size charged dust-particles are pre-v cipitated, and a final zone in which the remaining relatively smaller-size charged dust-particles are precipitated; in which precipitator-cell the various electrode-means comprising the zones are compactly arranged so that the overall dimensions of the cell are minimized.

It is a further. object of my invention to provide a precipitator-cell having dust-removing means including precipitator-electrodes upon which the precipitated dust collects, in which precipitator-cell the precipitator-electrodes can be thoroughly and effectively cleaned by a discharge of a cleaning liquid spread over the dustremoving means.

Still another object of my invention is to provide a precipitator-cell of such characteristics that a plurality of them can be readily arranged side by side in a housing to form a complete dustprecipitator.

A still further object of my invention is to provide a housing for a plurality of smaller precipitions of my invention, in addition to those heretoi'ore mentioned, will be discernible from the following description thereof which is to be taken in conjunction with the accompanying drawings. These drawings are on various scales, and some views have parts omitted in the interest of clarity of illustration. In these drawings:

Figure 1 is a side elevation, with parts broken away, of a precipitator-cell.

Fig. 2 is an end view of the gas-inlet end of the precipitator-cell.

Fig. 3 is a sectional view substantially on the line IIIIII of Fig. 1.

Fig. 4 is an elevational view of a relatively uninsulated or ground precipita'tor-plate utilized in the intermediate dust-precipitating zone.

Fig. 5 is an elevational view of a relatively insulated precipitator-plate associated with the precipitator-plate of Fig. 4.

Fig. 6 is an end view of a dust-precipitating means of the final zone, which is adapted to be inserted into the casing of the precipitator-cell.

Fig. 7 is a side view, with parts broken away, of the dust-precipitating means of Fig. 6.

Fig. 8 is an enlarged sectional view, taken substantially on the line VIII-VIII of Fig. 7, showing the manner in which the relatively insulated and uninsulated precipitator-plates of the dustprecipitatingmeans of Fig. 6 are assembled.

Fig. 9 is a side elevational view of a housing adapted to contain a plurality of precipitatorcells.

Fig. 10 is a plan view of the upstream portion of such housing, with its top wall removed.

Fig. 11 is an end elevational view of the housing and precipitator-cells therein, looking at it from the downstream side or outlet end.

Fig. 12 is a detail view showing means for fix ing the precipitator-cells in the housing, and

Fig. 13 is a schematic view of a system for sup- .plying cleaning liquid to the precipitator-cells for cleaning their various electrode-means.

Figs. 1 through 8 show generally the construction of a unit precipitator-cell adapted more particularly for cleaning an air-stream flowing in the direction of the arrows shown in Fig. l. The percipitator-cell is indicated in its entirety by the reference numeral I, and comprises an openended rectangular-prismatic casing 2 having a relatively flat bottom wall 3, a relatively flat top wall 4, and relatively flat side walls I and 6,

A relatively shallow liquid-distributing compertinent or chamber, indicated in its entirety by the reference numeral I, is formed substantially completely across the topof the casing-j,

' The chamber 1 is formed by the top wall 4 and a shallow pan 8 secured to the side walls 5 and 8 by a plurality of spaced countersunk screws 8 passing through walls of the pan and screwing into threaded holes in bars Ill secured across the inside walls of the pan. Pan 8 has a bottom wall provided with a large number of equally spaced perforations or holes l2 (Fig. 4) providing numerous liquid discharge-openings. downstream wall i3 of the chamber I is provided with a single liquid-inlet stub-pipe |4 adapted to be connected to a liquid-supply system.

The precipitator-cell includes a gas-cleaning or dust-removing means which comprises, in this embodiment, three zones inside the casing 2. A zone A, at the upstream end of the casing, is the ionizing or dust-charging zone; a zone B, immediately after the zone A in the direction of gas-flow, is a dustprecepitating zone which serves to remove the dust-particles of relatively larger size; and a. zone C, at the downstream end of the casing, is a second dust-precipitating zone which serves to remove charged dust-particles of relatively smaller size. The zone A, for charging the dust-particles in the gas stream, comprises cooperating discharging and nondiscliarging electrode-means; the zone B comprises a relatively few widely-spaced alternately relatively insulated and uninsulated precipitatingelectrodes in the form of relatively rigid plates; and the zone C comprises relatively closely spaced precipitating-electrodes in the form of plates which may be either rigid or somewhat flexible.

The discharging and nondischarging electrade-means of zone A form an ionizing means which comprises 9, plurality of spaced discharging ionizing wires 20 insulatedly supported between spaced tubular nondischarging groundelectrodes 2| and 22 and semicylindrical nondischarglng ground-electrodes 23 and 24. The ground-electrodes are equally spaced across the front end of the casing 2 with the ground-electrodes 23 and 24 unitary with the casing sizes 5 and 6, respectively. Each ionizing wire 20 is disposed substantially equi-distant from and between a pair'oi consecutive ground-electrodes. For supporting the ground-electrodes 2| and 22,

- the bottom wall 3 of the casing has secured 3| whose cross leg is bolted by a. bolt to awall of the chamber 1. Consequently, the ground-electrodes 2| and 22 can be removably supported in the casing 2.

The precipitating-electrodes of the dust-precipitating means of zone B comprises relatively insulated plates 35 and relatively unirisulated plates 36 arranged in alternate relation; :1 plate- 25 being in back of, or on the downstream side of, each ionizing wire 20, and a plate 34 in back oi. each'of the ground-electrodes 2| and 22,. The precipitator-plates 35 and 36 have been shown as planar and solid, but they. could obviously be 'bent or otherwise formed. The sides 5 and 6 of the casing 2, facing a plate 25, also function as precipitating-electrodes for this dust-precipitating means. Consequently there are as many precipitator-plates, in eflect, in zone B as there are electrodes in zone A.

A feature of my invention resides in a novel sub-assembly for the dust-charging means and dust-precipitating means of zones A and B, which permits it to be readily mounted in the casing 2 while at the same time keeping to a minimum the longitudinal length required for the zones A and B. To this end each of the ground-electrodes 2| and 22 has secured thereto a pair of insulators 40 and 4| spaced along its tumed end flanges and small intermediate metal angles secured thereto, to which the upstream edge portions of the plates 35 are symmetrically fastened by rivets or otherwise, each plate 3! being supported by both bars 43 and 44.

Each plate 35 has secured to each of its upstream comers a conducting arm .48 which extends upstream, the arms belng of such length that they terminate approximately at the place where the associated ionizing wire 20 is to be located. The associated ionizing wire 24 is strung between the arms 40 of each plate 25, and

is fastened thereto. Notches 41 are provided in the arms to facilitate securing the ends of the ionizing wires to the arms.

From the structure described, it is evident that the groundele'ctrodes 2| and 22, all the plates 35 and all the ionizing wires 2. are part 'of a subassembly supported by the ground-electrodes 2| and 22 inside the casing 2, with the plates 25 and ionizing wires 20 in conducting relation and properly insulated from the groundstantially the full height of the casing between electrodes and from the casing, because the plates 35 are shorter than the transverse dimension of the casing between the bottom wall I and the wall II, which define and guide the gas stream. A single connector-lead 44, secured to any insulated metallic part of the subessembly unit, can electrify or charge all-the ionizing wires and all the platps 35. In the embodiment disclosed, the conn tor-lead is secured to an arm 48, near the gas-inlet of the casing 2.

The relatively uninsulated or ground plate I. are somewhat longer and wider than the plates II. The plates 28 extend transversely for subthe bottom wall I and the wall ll of the chamher I; and extend longitudinally. in the gas-flow direction, beyond the plates II, The upstream edges r the plates is and I are transversely substantially aligned, the grounded plates 84 being provided with semicircular cutouts 40" about the bars 42 and 44 for providing adequate air-insulation between suchbars and the grounded plates. The cutouts 4| also permit the grounded plates 30 to be disposed longitudinally toward the'insulators 44 and 4| which support the insulated plates II. Each ground plate 34 is securedinsidethemingatitslowetedgemd anupper upstream corner.

. stead of being provided with grooves 61.

"ends.

The lower edge of each plate 66 is turned to provide a flange 49 having spaced holes therein through which each of which a screw 49' passes, the screw being countersunk in the exterior surface of the bottom wall 2 of the casing and provided with a nut for fastening the flange 49 to this bottom wall. Narrow metal upright angles 56 and 5| are secured respective to the side walls 5 and 6 of the casing, extending for substantially the internal height thereof; and a'narrow metal securing bar 52 is secured between and spans the angles 50 and 5|. The securing bar 52 has an edge near the wall ll of the chamber 1, and a fiat side spaced slightly from the downstream edges of the plates 36. Securing means comprising small angles 53 are fastened to the bar 52 and to an upper downstream corner of the plates 66, the angles 53 having elongated holes to accommodate variations in the disposition of the edges-of the plates 36.

The dust-precipitating means of zone C comprises another subassembly unit 59 (Figs. 68)

.having a relatively stiff bottom plate 66 to which are fastened relatively stiff outwardly flanged side plates 6| and 62. The alternately relatively insulated and uninsulated precipitator-plates 63 and 64,'respectively, are supportedbetween the sides 6| and 62, the sides 6| and 62 also functioning as relatively uninsulated precipitatorplates. The sides 6| and 62 and the plates 63 and 64 are each provided with a plurality of.

staggered holes, each of which receives a protuberance 65 of an insulating spacer 66 provided with an indentation groove 61 on its other side, which receives a protuberance 65 of the adjacent spacer, such protuberance 65 passing through an associated hole in a plate. The end spacers 66, however, for one side 62, are flat finished Tige ground plates 66 are longer in width and length than the insulated plates 66 and the edges of the former project beyond the edges of the latter substantially completely around their peripheries except at comers which are formed to permit a power source to be connected to each series of like plates. To this end a downstream corner of each ground plate 66 is trimmed as at 69 so that a corner of the insulated plates 66 ex-' tend outwardly beyond the trimmed corners thereat. Each corner 16 is provided with a slot or hole for receiving a conducting wire conductively secured to the insulated plates and terminating in a connector-lead 12.

' The ground plates 64 rest on the metal bottom plate 60, but to ensure a good electrical connection, a downstream corner of each insulated plate 63 is cut away and the protruding corners 13 thereat of the ground plates are conductively connected to a conducting wire 14 conductively secured to the sides 6| and 62.

For clamping the relatively insulated and uninsulated plates 66 and 64 between the sides 6| and 62, a side 62 may be provided with elongated holes in one of its flange 15, which isfastened to the bottom 66 by screws passing therethrough,

the side 62 sliding toward the side 6| as the two are clamped together by means of clamping rods I6, the side 6| being fixedly fastened to the bottom 66. No top is provided for the dust-precipitating means of zoneC, so that it is open at a top and on. its downstream and upstream The dust-precipitating means of zone C is of such size that when disposed in the casing 2 the upper edge thereof is closed to the bottom is close to the downstream end of the dust-precipitating means of zone B.

In assembling the precipitator-cell, angles 56 and 5|, bar 62 and the grounded plates 66 of zone B are secured in place. The subassembly unit built about the ground electrodes 2| and 22 is then fastened in place, the plates 35 sliding between the plates 36. The dust-precipitating assembly unit 59 for the zone C is then slid into the casing 2 from downstream end, with the flanges of the sides 6| and 62 abutting the angles 50 and 5| and the bar 52, and the bottom plate 66 of the subassembly unit}! resting on the bottom-wall 3 of the casing. One or more small adjustable clamps 11, associated with each of Q the casing side walls 5 and 6 and each of the sides 6| and 62 are utilized for fixing the subassembly unit 59 inside the casing. I

While each precipitator-cell is utilizable per se for gas cleaning, I prefer to provide a housing for a plurality of such cells, the housing being suitably constructed for correlation with the operating parts of the precipitator-cells.

Referring more particularly to Figs. 9-12, the housing 86 is open-ended in the gas-flow direction and is slightly longer in this direction than the precipitator-cells I supported in the housing side by side. The housing 80 has a bottom 6|, sloped downwardly in the direction of gas-flow, a top 6, sides 83 and 84, and suitable exterior reinforcing and supporting means 85 which are not shown in all the figures. brackets 86 are secured to certain members 65, so that completed dust-precipitator unit, embracing the housing 86, can be mounted in a suitable system. In this embodiment the housing is of such size that the completed dust-precipitator unit can be installed in the ventilating system of a Pullman lounge car.

The housing 60 is of a width to hold four precipitator-cells side by side, as shown in Fig. 11. The vertical upstream edges of the precipitatorcells are almost fiush with the upstream end of the housingbut because of the sloped bottom 6|, assume a slightly tilted position indicated by the dotted line 81 in Fig. 9. A plurality'of spaced fixed angles 86 (Fig. 10) are secured to the underneath downstream edge of the top 32 of the housing, each angle being adapted to be abutted by the vertical edges of a pair of adjacent casings 2 of adjacent precipitator-cell. Adjustably fastenable angles 89 abut the opposite edges of such sides, being movabl along the topwall for securely fixing the cells I in place. As shown in Fig. 12, each angle 89 may be secured to the top 82 of the housing by means of a bolt and screw device slidable in an elongated hole in the top 82. Any open spaces between adjacent precipitator cells I and between the precipitatorcells and the housing can be caulked to bar gasflow therethrough.

The downstream side of the housing extends beyond the cells to provide an end space in which wall ll of the chamber I, and the upstream end is disposed a liquid-supply pipe means 86 and bus-bar means, indicated, in its entirety by the reference numeral 8|, through which the relatively insulated plates of the dust-precipitating means of the zone C can be excited.

The liquid-supply means comprises a pipe 92 provided with a plurality of T's 62' and an elbow 98 which areconnected to the respective stub-pipes M of the liquid-distributing chamber I. The inlet end of the pipe 62 is adapted to be coupled to a flexible pipe connection 66' leading to a liquid-container 64 when the dust-precipi- In Fi 9, securing tator is to be cleaned, and is adapted to be uncoupled after such cleaning operation.

I prefer to use a viscous liquid, such as oil, for cleaning the various electrode-means of the dustprecipitator at suitable intervals. It is desirable to thoroughly wash the electrode-means without streaking. To accomplish this without increasing the cubic content of the completed dust-precipitator, I prefer to make the holes I2 in the bottom wall- II of the chamber I of small size, about .050 inch in diameter, and spaced about ,250 inch between centers. By supp g oil at low pressure to the oil-chambers I, the oil flows out of the holes l2, forming falling streams which fall mostly because" of gravity; but the upper ends or sources of these streams are not always underneath the holes but actually migrate about them, thereby completely covering the upper Ziongitudinal area of each precipitator-cell.

However, it is desirable to keep the supply of oil to the oil chamber I clean because the small holes I2 may otherwise quickly clog. Conse quently, I insert an oil filter 95 in the supplypipe connection 93', preferably before the pump 90 which pumps oil to the supply-pipe 92 for distribution to the various oil chambers 1. When the electrode-means are washed the oil discharged from the bottom II reaches the various electrodes of the precipitator-cell's, flowing downwardly to the bottom wall of the precipitator-cell and then into a transversely-sloped trough 91 at the upstream end of the housing 80 and a similarly sloped trough 98 on the downstream side of the housing, the slope of the bottom of the cells, which rest on the sloped bottom 8| of the housing, directing most of the oil to the trough 98. Outlet pipes 09 convey the used oil to an attachment I of a coupling to which can be connected and disconnected a flexible pipe connection I 0| leading back to the container 54.

sary to apply high voltage to the subassernblyv unit comprising the ionizing wires 20 and the precipitating-electrodes 35, and to apply high voltage to the precipitating-electrode 63.

To this end an insulator I02 is mounted at each side of the housing 80, at the downstream edge; being supported by a bracket I03 extending outwardly from the housing. The tops of the insulators I02 support a bus-bar I04 extendingacross the front of the housing, air-insulated therefrom. By connecting each connector-lead 40 of each precipitator-celltothis bus-ban, the ionizing wires 20 and the high voltage plates 35 canbecharged or energized. 1

The energizingmeans 9| ,at the rear end 'of the housing comprises a'pair of insulators 01' insulating bushings I05, each of which is respectively secured on the downstream protruding edge of the associated sidewalls 03 or 04 of the housing. "A conducting bus-bar I08 is secured to and spans the pair of insulators I05. By connecting the connector-leads I2 to-the various precipitator-cells to this bus-bar ,I0i the relatively lnsu'- lated precipitator-plates 03 can be charged.

From the foregoing it is evident that I have provided a very compact electrical dust-precipitator which can be easily and readily washed and can be properly suitably energized. The'spacing between the precipitating electrodes follows that described in the aforesaid G. W. Penney patent-application, and a unit such as herein described can clean a large volume of air relative to the volume of air cleaned by prior devices of similar size. Very little space is not utilized in the precipitator herein described, and by utilizing an external source of liquid-supply for cleaning the electrode-means the size of the dust precipitator unit is further reduced.

While I have described m invention in its present preferred form, it is obvious that the various teachings thereof areapplicable-to other forms and are subject to modification.

I claim as my invention:

1. A gas-purifying precipitator for electrically removing gas-borne dust-particles from a stream of flowing gas, comprising gas-duct means cornpris'ing a casing having a first wall and a pair of side walls angularly extending from the first wall, gas-cleaning means in said gas-duct means for charging gas-home dust-particles and precipitating charged dust-particles, said gascleaning means comprising a dust-precipitating means including a plurality of spaced alternately relatively insulated and uninsulated plateelectrodes between and substantially parallel to said side walls, fastening means for'substantially abuttingly securing an edge of the relatively uninsulated plate-electrodes to said first wall, and relatively narrow bar means secured to said side walls, spanning said plate-electrodes, for securing an opposite corner of said relatively uninsulated plate-electrodes.

2. A device of the class described, comprising n an open-ended substantially horizontal housin means for a. gas-flow, a plurality of precipitator- .cells upported side by side in said housing, each of said precipitator-cells comprising dust-charg sulated precipitating-electrodes of each of said precipitator-cells directly to the last said busbar means.

3. A device of the class described, comprising an open-ended substantially rectangular-prismatic housing for a gas-flow, said housing having substantially flat top, bottom and side walls, in excess of two substantially rectangular-prismatic individual precipitator-cells supported side by side in said housing, each of said precipitator-cells having therein a plurality of electrode-means for dust-charging and dust-precipitation, said precipitator-cells being of slightly less length in the longitudinal gas-flow direction than said housing,-an insulator means secured to walls of said housing which extend beyond said precipitator-cells in the line of gasflow, single relatively narrow bus-bar means supported by said insulator means across and outside of said precipitawr-cellstand connectormeans electrically connecting said bus-bar means to an electrode-means in each of said precipitator-cells.

4. A device of the class described, comprising ing a housing means for a substantially horizontal gas flow, said housing having a sloped bottom wall, a plurality of rectangular precipitator-cells supported on said bottom wall, side by side in said housing means, each of said precipitatorcells comprising dust-charging means and dustlprecipitating means, said dust-charging means comprising non-discharging electrode-means -and cooperat ng relatively insulated ionizing electrode-means, said dust-precipitating means comprising a plurality of spaced alternately relatively insulated and uninsulated upstanding precipitating-electrodes, distributing means for distributing a treating liquid over said preciptating-electrodes and the spaces therebetween, pipe-means for supplying liquid to said distributing means, collecting means, associated with said bottom wall, for collecting distributed liquid, and means for removing collected liquid from said collecting means.

5. A device of the class described, comprising a housing means for a substantially horizontal as flow, a plurality of rectangular precipitatorcells supported side by side in said housing means, each of said precipitator-cells compris-' ing dust-charging means and dust-precipitating means, said dust-charging means comprising nondischarging electrode-means and cooperatrelatively insulated ionizing electrodemeans, said dust-precipitating means comprising a plurality of spaced alternately relatively insulated upstanding and uninsulated precipitating-electrodes, said housing means having a sloped bottom wall, said precipitator-cells resting on said bottom wall, distributing means for distributing a treating liquid over said precipitating-electrodes and the spaces therebetween, pipe-means for supplying liquid from outside said housing means to said distributing means, and a common trough extending across an end of said housing means at the lower end of said sloped bottom wall, for collecting distribute liquid.

6. Means for charging dust-particles in a flowing gas-stream and for precipitating charged dust-particles from the gas-stream, comprising elongated ground electrode-means substantially transverse to the direction of gasflow, precipitating electrode-means, insulator means fastened solely to and between said ground electrode-means and saidv precipitating electrode-means for securing them together in relatively insulated relation, an ionizing electrode-means carried solely by said precipitating electrode-means substantially parallel to and in insulated discharging relation to said elongated ground electrode-means.

7. An electrical dust-precipitator comprising a casing having side walls, an elongated ground electrode-means, means for supporting said elongated ground electrode-means between a pair of said wide walls of said casing, insulating means carried by said elongated ground electrode-means, relatively insulated precipitating electrode-means supported solely by said insulating means, between said side walls, on the downstream side of said elongated ground electrode-means, and ionizing electrode-means supported solely by said relatively insulated precipitating electrode-means substantially parallel to and in insulated discharging relation to said elongated ground electrode-means.

8. An item for an electrical dust-precipitator,

comprising an ionizing electrode and a pair of spaced elongated non-discharging electrodes cooperative with said ionizing electrode for providing a dust-charging electrostatic field, insulating means carried solely by said pair of elongated electrodes, a plurality of spaced 'precipitating-electrodes, .and means extending transverse to saidelongated electrodes, attached to said insulating means, for supporting said precipitating-electrodes in insulated spaced relation with respect to said elongated electrodes.

9. An electrical dust-precipitator comprising wall-means for defining boundaries of a gas-flow path for a gas-stream, means for charging gasborne dust-particles and precipitating charged gas-borne dust particles, comprising ionizing electrode-means and non-discharging electrodemeans cooperative with said ionizing electrode means for providing a dust-charging electrostatic field, said non-discharging electrodemeans comprising a pair of spaced elongated electrodes, means associated with said wallmeans, for supporting said elongated electrodes in the gas-stream path, insulating means carried solely by said pair of elongated electrodes, a plurality of spaced precipitating-electrodes, means attached to said insulating means, spanning said precipitating-electrodes, for supporting them on the downstream side of said non-discharging electrode-means, in insulated spaced relation to said wall-means and said non-discharging electrode-means, and means secured to said precipitator-electrodes for supporting said ionizing electrode-means.

10. An electrical dustprecipitator comprising wall-means for defining boundaries of a gasfiow path for a gas-stream; upstream means for charging gas-borne dust-particles comprising a pair of spaced elongated electrodes transverse to the gas-stream path; insulating means secured to said spaced elongated electrodes; downstream precipitating means for precipitating charged gas-borne dust-particles, comprising a plurality of spaced alternately relatively insulated and uninsulated precipitator-plates; and means-for supporting said relatively insulated pre'cipitator-plates from said insulating means.

11. An electrical dust-precipitator comprising wall-means for defining boundaries of a gas-flow :path for a gas-stream; means for charging gasborne dust-particles comprising a pair of spaced elongated electrodes transverse to the gasstream path; insulating means comprising an insulator secured to and on the downstream side of each of said elongated electrodes; bar means secured to and across said insulators; precipitating means for precipitating charged gas-borne,

dust-particles, comprising a plurality of spaced alternately relatively insulated and uninsulated precipitator-plates; said bar means comprising I means for supporting said relatively insulated trodes to said wall-means; insulating means sesured to said spaced elongated electrodes; downstream precipitating means for precipitating charged gas-borne dust-particles, comprising a plurality of spaced alternately relatively :insulated and uninsulated precipitator-plates; means for supporting said relatively insulated precipitator plates from said insulating means; and means carried by certain of said relatively insulated precipitator-plates for supporting said ionizing electrode-means in insulated discharging relation to said non-discharging electrodeineans.

13. An electrostatic dust precipitator comprising wall-means for defining outer boundaries of a gas-flow path for a gas-stream; dust-charging means comprising ionizing electrodemeans and non-discharging electrode-means spaced from said wall-means; dust-precipitating means spaced from said dust-charging means, comprising precipitating electrode-means spaced irom said wall-means and spaced from said non-discharging electrode-means in a gas-flow direction; insulating means spaced from said wallmeans for insulating said non-discharging electrode-means with respect to said precipitating electrode-means, said insulating means comprising an insulator in the space between said non- -discharging electrode-means and said precipitating electrode-means, said insulator being in the gas-flow path, said insulating means comprising means for securing a portion of said insulator to said non-discharging electrodemeans, and comprising means 101' securing another portion oi said insulator, which is spaced irom said one portion, to said precipitating electrode-means, whereby said non-discharging electrode-means and said precipitating electrode-means may constitute a single item oi structure.

14. A structural item for an electrical dustprecipitator, comprising an elongated non-discharging electrode, a precipitating-plate spaced from said electrode; and insulating means (or relatively insulating said electrode with respect to said plate, said insulating means comprising an insulator between said electrode and said plate, said insulating means further comprising fastening means for securing a first portion of said insulator to said electrode and for securing another portion of said insulator, which portion is spaced from said first portion, to said plate, with an edge of the plate, nearest said electrode, and the length-direction of said electrode being in substantially parallel planes. I EDWARD H. R. PEGG. 

